In computer graphics, such as for movies and video games, it has always been difficult to create character eye action (or “eyelines”) that seem lifelike. Character eyes often act lifeless, having little sense of reality about them. Thus, comparing what the animator envisions while constructing an image with the final rendered images can often yield dramatically different results.
The problem is compounded by the fact that in society much time is spent talking to others, and much of this time is spent making eye contact. Accordingly, most people are in essence eye “experts” and one is very quick to notice if something is wrong with the eyes of the person being looked at. Walt Disney is alleged to have stated that the audience generally fixates on character eyes, and great effort must be expended on these objects for characters to be convincing.
In one eyeline model, eyeballs are modeled as partial spheres, with concentric bands comprising polygons forming the pupil, iris, and white of the eye. The polygons are then shaded with texture maps. For example, a hemispherical model of an eye may be formed by a number of quadrilaterals, shaded to appear as the pupil, iris, and white. Realism may be enhanced by including reflections on the eye of light sources.
In eye tracking, the angles used to point the eyes at an object generally are such that the optical axes of each eye converge on a target on the object. Even with this enhanced realism, computer-generated eyes are often unsatisfactory.
Thus there is a need for a better model of computer-animated eyes.